The objective of this proposal is to determine the extent to which structural and/or functional changes take place in the microcirculation of renal, cardiac, cerebral and pulmonary tissue which is transplanted into the cheek pouch of hypertensive recipients. The Grollman and spontaneous hypertensive hamster models will be used. The structural measurements will include measurements of vessel wall thickness and vessel density. The functional measurements will include microvascular responsiveness to physiologic (PO2, PCO2, changes in transmural pressure) and pharmacologic (norepinephrine, angiotensin, K+) stimuli as well as measurement of vascular permeability and leakiness. This study should provide unique information regarding the microcirculatory changes that take place in hypertension as well as their cause.